The present invention relates to novel 3-furyl sulfides.
Artificial flavoring agents for foodstuffs have received increasing attention in recent years. In many areas, such food flavoring agents are preferred over natural flavoring agents at least in part because of the uniform flavor that may be so obtained. For example, natural food flavoring agents such as extracts, essences, concentrates and the like are often subject to wide variation due to changes in the quality, type and treatment of the raw materials. Such variation can be reflected in the end product and results in unreliable flavor characteristics and uncertainty as to consumer acceptance and cost. Additionally, the presence of the natural product in the ultimate food may be undesirable because of increased tendency to spoil. This is particularly troublesome in convenience and snack food usage where such products as dips, soups, chips, prepared dinners, canned foods, sauces, gravies and the like are apt to be stored by the consumer for some time prior to use.
The fundamental problem in preparing artificial flavoring agents is that of achieving as nearly as possible a true flavor reproduction. This generally proves to be a difficult task since the mechanism for flavor development in many foods is not understood. This is notable is products having meaty, sweet meat, nutty and tomato-like flavor characteristics.
Reproduction of meaty, sweet meat, nutty and tomato-like flavors and aromas has been the subject of the long and continuing search by those engaged in the production of foodstuffs. The severe shortage of foods, especially protein foods, in many parts of the world has given rise to the need for utilizing non-meat sources of proteins and making such proteins as palatable and as meat-like as possible. Hence, materials which will closely simulate or exactly reproduce the flavor and aroma of sweet meat products including liver product are required. In addition, a need exists for imparting, modifying or enhancing nuttty and tomato-like nuances to foodstuffs.
Moreover, there are a great many meat containing or meat based foods presently distributed in a preserved form. Examples being condensed soups, dry-soup mixes, dry meat, freeze-dried or lyophilized meats, packaged gravies and the like. While these products contain meat or meat extracts, the fragrance, taste and other organoleptic factors are very often impaired by the processing operation and it is desirable to supplement or enhance the flavors of these preserved foods with versatile materials which have either meaty, sweet meat, nutty and/or tomato-like aroma and taste nuances.
U.S. Pat. No. 3,666,495 has to do with certain furan derivatives having desirable meat, roast meat and roasted fragrance and flavor notes. Among the furan derivatives disclosed in said patent are methyl (2-methyl-3-furyl) trisulfide obtained by the reaction of 2-methyl-3-furan thiol with methyl disulfur chloride at a temperature of from -60.degree. C to 0.degree. C, and methyl (2-methyl-3-furyl) disulfide obtained by reacting 2-methyl-3-furan thiol with methane sulfenyl chloride.
Such 3-furyl alkyl disulfides possess organoleptic properties different in flavor character and intensity from the 3-furyl sulfides of our invention.
U.S. Pat. No. 3,836,563 issued on Sept. 17, 1974 broadly discloses 3-furyl alkyl sulfides having the structure: ##SPC2##
wherein R.sub.6 ' may be alkyl such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl and n-nonyl (See Col. 4, lines 10-18) and R.sub.7 ', R.sub.8 ' and R.sub.9 ' are either hydrogen or alkyl. Such 3-furyl alkyl sulfides of U.S. Pat. No. 3,836,563 possess organoleptic properties different in flavor character and intensity from the 3-furyl sulfides of our invention.
The present invention provides novel 3-furyl sulfides for altering, modifying or enhancing the meaty, nutty or tomato flavor or aroma of foodstuffs. Briefly, the novel compounds of our invention are 3-furyl sulfides having the formula: ##SPC3##
wherein R.sub.2 and R.sub.3 are each selected from the group consisting of hydrogen and methyl, at least one of R.sub.2 and R.sub.3 being methyl.
Thus, for example, 3-furyl sulfides contemplated within the scope of our invention are:
______________________________________ 3-furyl Sulfide Compound Structure ______________________________________ (2-methyl-3-furyl) (2-pyridylmethyl)sulfide ##STR1## (2-pyridylmethyl)(2,5- dimethyl-3-furyl)sulfide ##STR2## ______________________________________
The 3-furyl sulfides of our invention can be prepared by a process comprising the step of:
i. Providing a 2-ene-1,4-dione having the structure: ##SPC4## PA1 ii. Intimately admixing said 2-ene-1,4-dione with a pyridine methyl thiol having the formual ##SPC5## PA1 thereby providing a substituted 2-thia substituted 1,4-dione having the structure: ##SPC6## PA1 iii. Cyclizing said 2-thia substituted 1,4-dione to form a substituted or unsubstituted 3-furyl sulfide having the formula: ##SPC7## PA1 Methyl thiazole alcohol (4-methyl-5-betahydroxyethyl thiazole); PA1 2-Methyl butanethiol; PA1 4-Mercapto-2-butanone; PA1 3-Mercapto-2-pentanone; PA1 1-Mercapto-2-propanone; PA1 Benzaldehyde; PA1 Furfural; PA1 Furfuryl alcohol; PA1 2-Mercaptopropionic acid; PA1 2-Methylfuran-3-thiol; PA1 2-Methyldihydrofuran-3-thiol; PA1 2-Methyltetrahydrofuran-3-thiol; PA1 2-Ethylfuran-3-thiol; PA1 2-Ethyldihydrofuran-3-thiol; PA1 2-Ethyltetrahydrofuran-3-thiol; PA1 2-Propylfuran-3-thiol; PA1 2-Isopropylfuran-3-thiol; PA1 2-Isopropyldihydrofuran-3-thiol; PA1 2-Isopropyltetrahydrofuran-3-thiol; PA1 2-Propyldihydrofuran-3-thiol; PA1 2,5-Dimethylfuran-3-thiol; PA1 2,5-Dimethyldihydrofuran-3-thiol; PA1 2,5-Dimethyltetrahydrofuran-3-thiol; PA1 2,5-Diethylfuran-3-thiol; PA1 2,5-Diethyltetrahydrofuran-3-thiol; PA1 2-Ethyl-5-methylfuran-3-thiol; PA1 2-Methyl-5-ethylfuran-3-thiol; PA1 2-Ethyl-5-methyldihydrofuran-3-thiol; PA1 2-Ethyl-5-methyltetrahydrofuran-3-thiol; PA1 2,5-Dipropylfuran-3-thiol; PA1 2,5-diisopropylfuran-3-thiol; PA1 5-Isopropyl-2-methylfuran-3-thiol; PA1 2-Butylfuran-3-thiol; PA1 2-Ethyl-5-propyltetrahydrofuran-3-thiol; PA1 Bis(2-methyl-3-furyl) sulfide; PA1 Bis(2-methyl-3-furyl) disulfide; PA1 Bis(2-ethyl-3-furyl) sulfide; PA1 Bis(2-ethyl-3-furyl) disulfide; PA1 Bis(2,5-dimethyl-3-furyl) sulfide; PA1 Bis(2,5-dimethyl-3-furyl) disulfide; PA1 Bis(2-methyl-3-dihydrofuryl) sulfide; PA1 Bis(2-methyl-3-tetrahydrofuryl) sulfide; PA1 Bis(2-methyl-3-tetrahydrofuryl) disulphide; PA1 Bis(2-methyl-3-dihydrofuryl) disulfide; PA1 Bis(2,5-diethyl-3-dihydrofuryl) sulfide; PA1 Bis(2,5-diethyl-3-furyl) sulfide; PA1 Bis(2-ethyl-5-methyl-3-furyl) disulfide; PA1 Bis(2,5-diethyl-3-furyl) disulfide; PA1 Bis(2,5-dipropyl-3-furyl)disulfide PA1 Bis(2,5-dipropyl-3-furyl) sulfide; PA1 Bis(2,5-dibutyl-3-furyl) disulfide; PA1 Bis(5-ethyl-2-methyl-3-dihydrofuryl) disulfide; PA1 Bis(2-isopropyl-3-furyl) sulfide; PA1 Bis(2-isopropyl-3-furyl) disulfide; PA1 Bis(2-isopropyl-3-dihydrofuryl) sulfide; PA1 Bis(2-isopropyl-3-tetrahydrofuryl) disulfide; PA1 Alkyl pyrazine; PA1 Methyl pyrazine; PA1 2-Ethyl-3-methyl pyrazine; PA1 Tetramethyl pyrazine; PA1 Dipropyl disulfide; PA1 Methyl benzyl disulfide; PA1 Alkyl thiophenes; PA1 2-Butyl thiophene; PA1 2,3-Dimethyl thiophene; PA1 5-Methyl furfural; PA1 Acetyl furan PA1 2,4-Decadienal; PA1 Guiacol; PA1 Phenyl acetaldehyde; PA1 .delta.-Decalactone; PA1 d-Limonene; PA1 Acetoin; PA1 Amyl acetate; PA1 Maltol; PA1 Ethyl butyrate; PA1 Levulinic acid; PA1 Piperonal; PA1 Ethyl acetate; PA1 n-Octanal; PA1 n-Pentanal; PA1 Hexanal; PA1 Diacetyl; PA1 Monosodium glutamate; PA1 Sulfur-containing amino acids; PA1 Cysteine; PA1 Hydrolyzed fish protein; and PA1 Tetramethyl pyrazine. When the 3-furyl sulfides according to this invention are used in order to enhance, modify, augument or alter the aroma or taste of tomato flavored foodstuffs or foodstuffs where tomato flavors are to be imparted, examples of preferred co-flavoring adjuvants are: PA1 2-isobutyl-thiazole; PA1 2-n-butyl-thiazole; PA1 2-phenyl-4-pentenal; PA1 2-phenyl-4-pentenaldimethyl-acetyl; and PA1 2-phenyl-4-pentenaldiethyl-acetal.
wherein R.sub.2 and R.sub.3 are each hydrogen or methyl; at least one of R.sub.2 and R.sub.3 being methyl. Either R.sub.2 or R.sub.3 may be hydrogen in the event that in step (ii) the 2-ene-1,4-dione is admixed with the thiol in the presence of an organic base such as piperidine, pyridine, triethyl amine, quinoline or alpha-picoline or a mixture thereof.
The 2-ene-1,4-dione may be prepared by reacting 2,5-dialkoxy-2,5-dialkyl-2,5-dihydrofuran with a weak acid hydrolysis agent such as 1% aqueous acetic acid under reflux conditions. The resulting material will be in the case of starting with 2,5-dimethoxy-2,5-dimethyl-2,5-dihydrofuran, cis-3-hexen-2,5-dione.
The resulting 2-ene-1,4-dione is then reacted with the thiol, an example of which is 1-mercaptomethyl-pyridine.
The reaction may be carried out in a solvent such as water or an ether such as diethyl ether or a hydrocarbon such as benzene or hexane or cyclohexane. The reaction may also be carried out without the use of a solvent. The reaction may be carried out under reflux conditions, although temperatures varying from 0.degree. up to 60.degree. C are suitable and will give rise to commercially suitable yields.
The aforementioned 2-thia substituted 1,4-diones are then cyclized to form substituted or unsubstituted 3-thia furans according to the following reaction: ##SPC8##
wherein R.sub.2 and R.sub.3 are defined as above. The resulting 3-furyl sulfides (novel compounds of our invention) are used for their organoleptic properties.
The cyclization reaction carried out in cyclizing the 2-thia substituted 1,4-dione is carried out in the presence of a cyclization agent, preferably, isopropenyl acetate. The cyclization is also carried out in the presence of such a catalyst as concentrated sulfuric acid, zinc chloride, boron triflouride, aluminum trichloride, and para-toluene sulfonic acid, each of these being acid catalysts. Preferably, the ratio of isopropenyl acetate to 2-thia substituted 1,4-dione is 4 or 5:1. The ratio of acid catalyst to isopropenyl acetate is from 0.001 up to 0.05 (mole ratio). The cyclization reaction may be run at temperatures of between 25.degree. C up to reflux at atmospheric pressure (96.degree. C). Still greater reflux temperatures may be used if the pressure is greater than atmospheric. Furthermore, in place of isopropenyl acetate as a cyclization agent, acetic anhydride or propionic anhydride may be used. The mole ratio of cyclization agent to 2-thia substituted 1,4-dione is preferably 4 to 5:1.
The reaction product is then purified by appropriate extraction and distillation techniques.
The 3-furyl sulfides of our invention can also be prepared by reacting 3-furan thiols, e.g. 2-methyl-3-furan thiol with an .alpha.-picolyl halide (2-pyridyl-methyl halide) (e.g. a bromide or chloride); (i) in the presence of a base such as an alkali metal alkoxide (e.g., sodium methoxide); (ii) at a temperature in the range of 15.degree.-65.degree. C; and (iii) in a suitable solvent, e.g., an anhydrous lower alkanol such as anhydrous methanol, ethanol or isopropanol. Thus, for example, .alpha.-picolyl chloride hydrochloride, when reacted with 2-methyl-3-furan thiol in anhydrous methanol in the presence of sodium methoxide at a temperature of 24.degree. C will yield (2-methyl-3-furyl) (2-pyridylmethyl) sulfide.
The following compounds of our invention produced using the above processes have useful organoleptic properties giving rise to their use as foodstuff flavors as set forth in an illustrative manner in the following table:
TABLE I __________________________________________________________________________ 3-Furyl Sulfide Compound Structure Flavor Properties __________________________________________________________________________ (2-methyl-3-furyl) (2-pyridylmethyl) sulfide ##STR3## Sweet and meaty aroma and a sweet meaty and nutty flavor with metallic and mouthfeel nuances. (2-pyridylmethyl) (2,5-dimethyl-3- furyl)sulfide ##STR4## Tomato-like nuances and sweet meat nuances. __________________________________________________________________________
The 3-furyl sulfides according to the present invention can be used to alter, vary, fortify, modify, enhance or otherwise improve the organoleptic properties, including flavor and/or aroma, of a wide variety of materials which are ingested, consumed or otherwise organoleptically sensed. The term "alter" in its various forms will be understood herein to mean the supplying or imparting a flavor character or note to an otherwise bland, relatively tasteless substance, or augmenting an existing flavor characteristic where the natural flavor is deficient in some regard, or supplementing the existing flavor or aroma impression to modify the organoleptic character. The materials which are so altered are generally referred to herein as consumable materials.
The term "enhance" is used herein to mean the intensification of a flavor or aroma characteristic or note without the modification of the quality thereof. Thus, "enhancement" of a flavor or aroma means that the enhancement agent does not add any additional flavor note or nuance.
Such 3-furyl sulfides of this invention are accordingly useful in flavoring compositions. Flavoring compositions are herein taken to mean those which contribute a part of the overall flavor impression by supplementing or fortifying a natural or artificial flavor in a material, as well as those which supply substantially all the flavor and/or aroma to a consumable article.
The term "foodstuff" as used herein includes both solid and liquid ingestible materials for man or animals, which materials usually do, but need not, have nutritional value. Thus, foodstuffs include meats, gravies, soups and convenience foods, vegetables, snack foods, dog and cat foods, other veterinary products and the like.
When the 3-furyl sulfides according to this invention are used in a food flavoring composition, they can be combined with conventional flavoring materials or adjuvants. Such co-ingredients or flavoring adjuvants are well known in the art for such use and have been extensively described in the literature. Apart from the requirement that any such adjuvant material be ingestibly acceptable, and thus non-toxic or otherwise non-deleterious, conventional materials can be used and broadly include other flavor materials, vehicles, stabilizers, thickeners, surface active agents, conditioners, and flavor intensififiers.
When the 3-furyl sulfides of our invention are used to modify or enhance or alter the aroma or taste of meat flavored substances or substances to be meat flavored, examples of preferred co-flavoring adjuvants are:
The 3-furyl sulfides or the compositions incorporating them, as mentioned above, can be combined with one or more vehicles or carriers for adding them to the particular product. Vehicles can be edible or otherwise suitable materials such as ethyl alcohol, propylene glycol, water and the like. Carriers include materials such as gum arabic, carrageenan, other gums and the like. The 3-furyl sulfides according to this invention can be incorporated with the carriers by conventional means such as spray-drying, drum-drying, and the like. Such carriers can also include materials for coacervating the 3-furyl sulfides (and other flavoring ingredients, as present) to provide encapsulated products. When the carrier is in emulsion the flavoring composition can also contain emulsifiers such as mono- and diglycerides of fatty acids and the like. With these carriers or vehicles, the desired physical form of the composition can be prepared.
The quantity of 3-furyl sulphide(s) utilized should be sufficient to impart the desired flavor characteristic to the product, but on the other hand, the use of an excessive amount of the derivatives is not only wasteful and uneconomical, but in some instances too large a quantity may unbalance the flavor or other organoleptic properties of the product consumed. The quantity used will vary depending upon the ultimate foodstuff; the amount and type of flavor initially present in the foodstuff; the further process or treatment steps to which the foodstuff will be subjected; regional and other preference factors; the type of storage, if any, to which the product will be subjected; and the preconsumption treatment, such as baking, frying, and so on, given to the product by the ultimate consumer. Accordingly, the terminology "effective amount" and "sufficient amount" is understood in the context of the present invention to be quantitatively adequate to alter the flavor of the foodstuff.
It is accordingly preferred that the ultimate compositions contain from about 0.0001 parts per million (ppm) to about 250 ppm of 3-furyl sulfides. More particularly, in food compositions, it is desirable to use from about 0.0005 ppm to 100 ppm in enhancing or modifying or imparting flavors and in certain preferred embodiments of the invention, from 0.2 to 50 ppm of the derivatives are included to add positive flavors to the finished product. All parts, proportions, percentages, and ratios herein are by weight unless otherwise indicated.
The amount of 3-furyl sulfides of our invention to be utilized in flavoring compositions can be varied over a wide range to the foodstuff. Thus, amounts of one or more derivatives according to the present invention of from about 2 ppm up to 80 percent of the total flavoring compositions can be incorporated in such compositions. It is generally found to be desirable to include from about 10 ppm up to about 20 percent of the 3-furyl sulfide in such compositions.
The following examples are given to illustrate embodiments of the invention as it is preferred to practice it. It will be understood that these examples are illustrative and the invention is not to be considered as restricted thereto except as indicated in the appended claims.